Tips and Tricks 319
8.4 Minimally Invasive Two-Incision
Total Hip Replacement using large Diameter
T.-R. Yoon, C.-I. Hur, S. Diwanji and D.-S. Lee
Background: Our experience with the minimally invasive (MI) two-incision
technique over the last 4 years has shown that total hip arthroplasty (THA) can be
performed safely and effectively in properly selected patients. Total hips with
larger-diameter femoral heads are more resistant to dislocation. The purpose of
the present study was to evaluate the short-term results of a minimally invasive
two-incision THA Using Large Diameter Ceramic-on-Ceramic Articulation.
Patients and Methods: A consecutive series of 50 patients who underwent
unilateral MI two-inicision THA from June 2006 to October 2006 were studied.
There were 35 men and 15 women with a mean age at arthroplasty of 44.9 years
(range, 23 to 73 years). There were 36 left and 14 right hip arthroplasties
performed. Indications for THA were avascular necrosis of the femoral head in 29
cases, osteoarthritis in 12 cases, rheumatoid arthritis in 3 cases, femur neck
fracture in 2 cases, dysplastic hips in 2 cases and ankylosing arthritis in 1 case. A
modified two-incision approach was used for all procedures in lateral position. In-
hospital data were collected retrospectively, and the initial postoperative
radiographs were analyzed. Twenty-eight patients received 36 mm diameter
femoral heads, while 22 patients received 32 mm diameter heads.
Results: All patients could mobilize in the following days after surgery. There was
no case of intraoperative complications such as intraoperative fracture, nerve
palsy, or vascular injury. Postoperatively there was no dislocation or deep vein
thrombosis. All femoral stems were inserted neutral or within 5 degree valgus. In all
patients, leg length discrepancy was within 5mm difference. The average ROM
of hips at last follow-up was significantly improved compared with the
Conclusion: Short-term results of a minimally invasive two-incision THA using
large diameter ceramic-on-ceramic articulation were excellent.
Although total hip arthroplasty remains the cornerstone of surgical treatment of
degenerative joint disease, dislocation continues to be a relatively common
complication of the procedure, second in frequency only to late prosthetic
loosening . Approximately 80 % of all dislocations following total hip
replacement occur in a posterior direction, with a reported prevalence of 0.7 to
5.5 % following primary surgery and 5 to 20 % following revision . The
contributing causes to total hip dislocation are reported to include femoral
component stem design , acetabular component orientation [1,22], surgical
approach , soft tissue laxity , femoral component head size , and
patient factors .
320 SESSION 8.4
Minimally invasive total hip arthroplasty is an alternative to traditional total hip
arthroplasty as it offers the patient a smaller incision, less rehabilitation time, and
better functional recovery. The benefits of the two-incision total hip arthroplasty
over the traditional or mini-single procedures include faster physical therapy and
rehabilitation with immediate weight bearing. The dislocation rate is theoretically
less with this procedure and patients can resume activities of daily living such as
return to work, driving, and recreational activities much sooner. But, this two-
incision technique is a technically demanding procedure.
It is generally appreciated that the range of motion of the artificial hip prior to
impingement increases with an increase in the diameter of the femoral head
because of the corresponding increase in the ratio of the head and neck
diameters. However, with the increasing recognition that osteolysis is a major
cause of long-term failure of total hip replacements, many authors have
advocated the routine use of femoral heads of smaller diameter to reduce the
volumetric wear rate when polyethylene liner is used. With the advent of
alternative bearings, such as a metal-on-metal or ceramic-on-ceramic
articulation, the use of larger femoral head size may provide increased stability
while not compromising the wear properties.
This study was undertaken to determine the short term results of a modified
minimally invasive two-incision total hip replacement using large diameter
Materials and Methods
A consecutive series of 50 patients who underwent unilateral MI two-inicision
THA from June 2006 to October 2006 were studied. There were 35 men and 15
women with a mean age at arthroplasty of 44.9 years (range, 23 to 73 years).
There were 36 left and 14 right hip arthroplasties performed. Indications for THA
were avascular necrosis of the femoral head in 29 cases (58 %), osteoarthritis in 12
cases (24 %), rheumatoid arthritis in 3 cases (6 %), femur neck fracture in 2 cases (4
%), dysplastic hip in 2 cases (4 %) and ankylosing arthritis in 1 case (2 %). A modified
two-incision approach was used for all procedures in lateral position. In-hospital
data were collected retrospectively, and the initial postoperative radiographs
were analyzed. Twenty-eight patients (56 %) received 36 mm diameter femoral
heads (Fig. 1), while 22 patients (44 %) received 32 mm diameter heads (Fig. 2).
Mean body mass index (BMI) was 23.0 (range, 16 to 29). Mean patient weight and
height was 64.7 kg (range, 40 to 88 kg) and 167.4 (range, 148 to 186 cm),
respectively. Mean radiologic follow-up period after the index operation was 8.7
months (range, 6.3 to 10.9 months). All operations were performed by single
surgeon (TRY) using the modified MI two-incision approach. Anesthesia method
was epidural in 23 cases (46 %) and general in 27 cases (54 %).
All patients had placement of a cementless acetabular shell with porous
coating. Acetabular components inserted were truncated alumina ceramic
acetabular components, a ceramic head (BIOLOX®, Osteo AG, Selzach,
Switzerland) and ceramic liner. Acetabular cup diameter was 44 mm in 3 cases
(6 %), 46 mm in 6 cases (12 %), 48 mm in 13 cases (26 %), 50 mm in 6 cases (12 %),
Tips and Tricks 321
52 mm in 15 cases (30 %), 54 mm in 7 cases (14 %). All cementless femoral stem
inserted was M/L taper® stem (Centerpulse Orthopaedics, Baar, Switzerland).
(A, B) Preoperative anteroposterior
(AP) radiograph and femoral head
lateral radiograph show a patient
with avascular necrosis of left hip.
(C, D) He was operated with a
36mm ceramic femoral head
articulating with ceramic insert. In
the last follow-up, he can put on a
Budda position and walk without
any discomfort or limping.
(A, B) Preoperative anteroposterior
(AP) radiograph and femoral head
lateral radiograph show a patient
with avascular necrosis of left hip.
(C, D) He was operated with a
32mm ceramic femoral head
articulating with ceramic insert. In
the last follow-up, he can also put
on a Budda position and walk
without any discomfort or limping.
Landmarks for the skin incision such as the tip, anterior and posterior border of
the greater trochanter and trochanteric (vastus) ridge were identified. The first
incision was made over the anterolateral aspect of the hip ranging from 6-8 cm.
The incision started from the point approximately one finger breadth posterior to
anterior border of trochanter and just distal to trochanteric crest, extending
cranially and anteriorly at an angle of 30 degrees to the long axis of femur. The
incision roughly aimed at a point on iliac crest 3 cm posterior to the anterior
superior iliac spine (Fig. 3). Subcutaneous tissue and fascia lata were divided in
the anterior border of the gluteus medius was palpated at its insertion on the
greater trochanter. Intermuscular dissection between the gluteus medius and
322 SESSION 8.4
tensor fascia lata was done, carefully ligating lateral circumflex femoral vessels.
After anterior joint capsule was incised, femoral neck was osteotomised and
femoral head was removed.
For better visualization of the acetabulum, one or two Steinmann pins were
inserted at the posterosuperior side of the acetabulum to retract the gluteus
medius. Additionally, two or three curved Hohmann retractors were placed around
the acetabulum, usually anteroinferiorly, posteroinferiorly and inferiorly (Fig. 4). After
exposing the acetabulum as shown in Figure 4, reaming was performed.
Photograph showing landmarks (greater
trochanter, vastus ridge, anterior superior
iliac spine) and sites of anterolateral and
posterolateral skin incision.
For better view of acetabulam, one
Steinman pin and three curved Hohmann
retractors are placed around the
The posterior skin incision was then placed over the posterolateral aspect of
hip. The hip was flexed to 90 degrees and 4 to 6 cm incision was made over the
greater trochanter. After dissection through the muscle fibers of gluteus maximus,
the fat layer separating gluteus maximus and medius was exposed. The piriformis,
which was the landmark for the intermuscular dissection, was identified after
excising the fat (Fig. 5). The intermuscular dissection between fibers of piriformis
and gluteus medius led to joint capsule. Under direct visualization joint capsule
was incised on the posterosuperior side of the hip joint. A starting reamer was
introduced in to the femoral canal. After preparing the proximal femur with rasp,
size of femoral component was determined under fluoroscopy and femoral
component was inserted (Fig. 6). Femur was then brought anteriorly with traction,
external rotation and extension of the hip. With hip in external rotation and bone
hook around the neck, trial femoral head was inserted through anterior incision.
After trial reduction was performed, leg length and range of motion of hip joint
Tips and Tricks 323
were evaluated by both clinically and under fluoroscopy (by comparing the level
of the lesser trochanters with obturator foramina). The appropriate size final
femoral head was inserted and joint was reduced. In case of tight soft tissues,
sometimes it may not be possible to reduce the joint after insertion of a large
femoral head component. In that situation, we first put the femoral head in to the
acetabular cup and then engage the trunion in to the head with traction and
gentle manipulation. Leg length and range of motion was checked again.
Negative suction drain was placed and the posterior joint capsule, the anterior
joint capsule, fascia lata and subcutaneous tissue were repaired and the skin was
closed (Fig. 7).
This photograph shows piriformis as
a landmark for intermuscular
dissection between gluteus medius
(A) Through the posterior incision,
femoral stem is inserted and (B)
final evaluation of its position is
made with fluoroscopy.
photograph showing the
postoperative incision wound
of minimally invasive two-incision
total hip replacement.
324 SESSION 8.4
Postoperative protocol included abduction pillow between two legs to
prevent dislocation, and elastic stockings and limb mobilization to prevent deep
vein thrombosis. Quadriceps strengthening exercises were started on the same
day and sitting by the side of the bed was also allowed on the day of surgery if
patient was comfortable. Mobilization was recommended with tolerable weight
bearing on postoperative day one, if patient’s general condition is allowed. All
the patients were discharged home when they were safely able to mobilize with
an ambulatory aid.
All hips were evaluated preoperatively and at last follow-up using the Harris hip
score and WOMAC score. Patients specifically were asked about episodes of
instability or dislocation that could have been treated elsewhere. Other studies
investigated were range of motion of hips, hospital stay, operation time,
fluoroscopy time, blood loss by checking the hemoglobin and hematocrit
changes and intraoperative or postoperative complications. In the immediate
postoperative period, patients’ rehabilitation processes were checked. For some
patients who were unable to return for a last follow-up visit, the hip function were
evaluated by telephone interview.
A complete radiographic follow-up series, including preoperative,
postoperative, and last follow-up radiographs, was available for 50 hips. All
radiographic measurements were made by two investigators (CIH, DSL) other
than the senior investigator who did 100% of the surgeries. Radiographic exams
included an anteroposterior and frog lateral view of the hip. These views
determined acetabular anteversion angles and allowed a assessment of the
component position. The latest follow-up radiographs were assessed and
compared with the original postoperative radiographs to determine component
orientation, evidence of bony ingrowth, possible component migration, fracture,
dislocation, and/or mechanical failure.
The average time of clinical follow-up and examination was 8.7 months (range,
6.3 to 10.9 months). Hemoglobin level was changed from preoperatively 11.7
(range, 8.8 to 15.5) to 10.2 (range, 6.9 to 12.8), postoperatively. Hematocrit levels
were changed from 35.2 % (range, 26.3 to 46.8 %) to 30.6 % (range, 21.4 to 39.1%).
Mean operation time was checked 71 minutes (range, 48 to 91 minutes). Mean
intraoperative fluoroscopy exposure time was 6 seconds (range, 2 to 11 seconds).
The average Harris Hip Score (HHS) and WOMAC scores at last follow-up were
significantly improved compared with the preoperative scores (83 and 47 points
versus 3537 and 93 points, respectively). Also, the average ROM of hips at last
follow-up was significantly improved when compared with the preoperative
values (Table 1). Two cases would squat down because of ankylosing spondylitis
in one and CVA sequela in one. Four cases could not take Buddhist position
because of multiple fractures in two, ankylosis spondylitis in one and CVA history
in one. No case developed hip dislocation and needed further surgery.
Tips and Tricks 325
Preoperative Hip ROM Postoperative Hip ROM
Flexion 95.5° 113.1°
Internal rotation 2.2° 22.3°
External rotation 28.8° 56.7°
Abduction 21.7° 38.8°
Adduction 14.0° 24.9°
The average ROM of hip at last follow-up was compared with preoperative values.
Radiographically, the median acetabular shell abduction and anteversion
were 36º (range, 27 to 48 º) and 17 º (range, 5 to 32 º), respectively. There was no
evidence of cup migration. There was no fracture of the femoral component.
Average stem position was valgus 1.9 º (range, varus 2.3 º to valgus 4.8 º). In all
cases, the stem position was within the valgus or varus 5 º. There were no
complications intraoperatively or postoperatively.
Postoperatively, the average amount of hemovac drainage was 740cc and
average transfusion was 384cc. All patients could ambulate on the first
postoperative day with tolerable weight bearing. Rehabilitation proceeded with
initial walker ambulation postoperative 1.6 days and then, crutch ambulation
was started within the 6.5 days, and ambulation without any support was possible
after mean 9.3 days postoperatively. Climbing up the stairs without assistant
device was possible within 29.5 days on average, postoperatively.
Wear at the articulation as a result of the increasing demands in active and
young patients remains a significant clinical challenge. Age and activity level are
among the most important predictors of wear after THA. Despite the
improvement of implant, wear and osteolysis resulting in failure of the THA remain
significant concerns. Ceramics were introduced in total hip replacement to
address the problems of friction and wear that were reported with metal-on-
polyethylene articulations. This very hard and wettable material can limit wear
debris production and provide longer lifetime of the artificial hip after
implantation. Recent studies have reported the efficacy of using ceramic-on-
ceramic or metal-on-metal bearing surfaces, particularly in high-demand
patients. The alumina-on-alumina combination currently is being recognized as
one of the best answers to wear debris-induced osteolysis and is best used in
young and active patients .
However, one of the most publicized limitations of ceramic articulation is
implant fracture. The fracture rate of ceramics was 13.4% for implants
manufactured before 1990, fracture rate has decreased and now ranged from
0.2% to 5.7% due to development of technology [9,16,17,18]. D’Antonio and
Capello  reported no case of ceramic articulation fracture in over 950 THAs in
their large prospective study series. Some authors described that the principle
causes of ceramic fracture were related not to the material or manufacturing but
to surgical techniques . The limitations for the use of this material are an extra
326 SESSION 8.4
small socket , the need for a small head , and osteoporotic bone . In our
study, all cases used ceramic-on-ceramic articulation and no cases developed
implant fracture until this short period of follow-up.
Dislocation is a common complication after THA  and can severely disrupt
a patient’s quality of life. Early dislocation is a frequent problem following primary
THA. The prevalence of early dislocation following primary arthroplasty has been
reported less than 1% to 5% [19,27]. Late dislocation, occurring many years after
THA, is an increasing problem  and, in one study the prevalence increased by
1% every 5 years with a 22 mm femoral head . The patient risk factors for
dislocation after primary THA have been reported to be age 75 years or older,
preoperative diagnosis of femoral neck fracture or nonunion, chronic neurologic
disorders and a prior history of alcohol abuse [4,20,25,26]. The major factors of
prevention of dislocation are proper orientation of both the acetabular and
femoral component. Therefore, the use of larger femoral head to hip arthroplasty
adds to improve hip stability, and increase hip ROM and therefore lower the
incidence of dislocation [7,10]. The cause of dislocation is often secondary to
impingement. The type of impingement depends on the size of the femoral head.
With 22mm femoral heads, impingement between components occurs, most
often between the femoral neck and the acetabular component . With
femoral head larger than 32mm in diameter, bony impingement symptoms
commonly occur between the proximal femur and pelvis. This is because the
head to neck ratio increases as the size of the femoral head increases, which
allows a greater arc of curvature before the neck can make contact with the
acetabulum at the extremes of motion. The jump distance (the distance the
head must travel to disengage from the socket) is higher with a larger femoral
head, which is more stable against dislocation. Thus, the larger femoral head
adds substantially more stability to the hip reconstruction [7,10]. In our study, no
case developed hip dislocation even they were allowed for squatting and all
cases except two cases could squat.
The use of large diameter femoral heads in THAs with metal on polyethylene
articulation is limited because of wear. Studies have shown a higher volumetric
polyethylene wear rate with conventional UHMWPE articulating with a larger
diameter femoral head . The issue of increased wear must play a major role
in the decision making process. Historically using a larger head and thinner
polyethylene liner may not have been optimal because this patient has a higher
risk for revision surgery/liner exchange during his/her lifespan. However, a larger
femoral head is an attractive choice when stability is a critical factor and wear is
not a major concern such as ceramic-on-ceramic articulation. In our study, we
could not estimate the effect of large diameter femoral head regarding the wear
and osteolysis because of short follow up duration.
The benefits of minimally invasive two-incision total hip arthroplasty include a
smaller incision and minimal soft tissue injury than with the traditional posterior
approach, therefore use of minimally invasive decreases hospital stay and
permits quicker recovery. In our study with the use of two-incision minimally
invasive THA, the patients’ recovery was much quick and stability was better
which was proved by increased ROM and possibility of squatting position in most
patients. Also, there was no dislocation with this procedure and patients could
resume activities of daily living such as return to work, driving, and recreational
activities much sooner . We believe that two-incision technique, because of
its complete muscle-preserving technique is the most advantageous approach
Tips and Tricks 327
to date for better functional recovery if the surgery is performed by experienced
Our data suggest that 32 and 36 mm femoral heads with ceramic-on-ceramic
articulation notably reduce the prevalence of early dislocation after primary THA,
especially in combination with the modified two-incision minimally invasive THA
approach when compared to historical controls. To date, no patient with a larger
femoral head in primary THA has undergone revision for recurrent dislocation in
A minimally invasive two-incision THA using large diameter ceramic-on-
ceramic articulation is excellent method that prevents dislocation, has good
functional and clinical results and faster recovery.
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